1. Field of the Invention
The present invention relates to a light source device and a display apparatus, and more particularly to a backlight module and a display apparatus.
2. Description of Related Art
Recently, with the advantages of small volume, light weight, low drive voltage, low power consumption, a wide range of applications in notebook, camera, television and other electronic image device, the liquid crystal display (LCD) has replaced the cathode ray tube (CRT).
Generally, the LCD comprises an LCD panel and a backlight module. The LCD panel displays an image through the twist of liquid crystal molecules and the polarizing plates to change the transmittance in different regions. Since the liquid crystal molecules do not emit light, a backlight module is needed to provide a light source. The backlight module can be divided into a side type backlight module and a direct type backlight module. In order to achieve uniform light mixing effect, a longer light mixing distance for the direct type backlight module is needed, so that the direct type backlight module has a thicker thickness. Thereby, the direct type backlight module is not suitable for a thinness LCD, while the edge type backlight module has an advantage for thinning.
As development of large size and high contrast of the LCD, a backlight module which using local dimming is provided to achieve high dynamic contrast display effect. In addition, comparing with the direct type backlight module, the edge type backlight module having a joining type light guide plate configuration, which using local dimming, is more suitable for thinning.
FIG. 1 is a schematic view illustrating a conventional backlight module. Referring to FIG. 1, a backlight module 100 is composed of a plurality of light guide plates 110 which are joined together, and a local dimming is used to achieve high dynamic contrast display effect. As FIG. 1 shown, the light source set 120a of the light guide plate 110a in a display region is lit, and the light source sets 120 of the light guide plates 110 in a non-display region are turned off, such that the contrast of the LCD is increased. However, when the above mentioned local dimming is performed, a joining boundary is easily displayed on an image because the light guide plates have different brightness, so as to deteriorate the display quality.
In order to resolve the above problem, a method of increasing the number of the local dimming regions of a backlight module is provided. However, if the number of the local dimming regions is increased, the number of light guide plates, the number of local dimming driving chips, and the difficult of processing the image are increased, and thus the manufacturing cost is increased. Another method of additionally adding optical films having diffusing function in a backlight module is also provided to resolve the problem of showing the joining boundary on a displayed image. However, with this method, the weight of the backlight module and the cost are increased, and the total brightness of the backlight module is reduced. Thereby, the number of light sources or the driving power is needed to increase to compensate the brightness loss from the additional added optical films. As a result, the power consumption of the backlight module is increased.